Northern Vietnam is expected to experience a spell of thunderstorms, lightning and possible extreme weather due to weak cold air, before a second heatwave of 2026 arrives with potentially severe intensity.

According to the National Center for Hydro-Meteorological Forecasting, as of April 3, a weak cold air mass in the north is continuing to move, compressing a low-pressure trough and pushing it gradually southward.

From late afternoon through the early morning of April 4, the northern region - excluding Dien Bien and Lai Chau - is forecast to see scattered showers and thunderstorms, with rainfall ranging from 10 to 20 mm, and localized downpours exceeding 40 mm.

During thunderstorms, there is a high risk of tornadoes, lightning, hail and strong gusts. Intense localized rainfall may trigger flash floods on small rivers and streams, as well as landslides in mountainous areas.

Meteorological experts warn that during seasonal transitions, strong storms accompanied by whirlwinds and hail are common. These are caused by the interaction between hot and cold air masses, combined with strong upper-level westerly winds at altitudes of 3,000-5,000 meters.

Such phenomena can develop rapidly and pose serious risks. Within minutes, strong winds can rip off roofs and uproot trees; lightning can directly threaten lives; and hail can damage crops, vehicles and infrastructure.

Experts note that while cold air will continue to appear in April, it will mainly act to compress low-pressure systems and trigger transitional storms in northern Vietnam. Authorities and residents are therefore advised to remain vigilant against extreme weather.

Second heatwave expected to intensify and persist

From April 4 onward, temperatures in the North are expected to rise sharply.

Notably, from around April 6, a widespread heatwave is likely to affect the northwestern region and the Red River Delta. By April 7, the heat is expected to expand further into northeastern areas.

In Hanoi, weak cold air will bring rain tonight and into early April 4. After that, temperatures are forecast to rise by around 4 degrees Celsius on April 5, before entering a prolonged period of heat from April 6 onward, including days of intense heat.

Meanwhile, on April 4, areas from Quang Tri to Quang Ngai will experience hot conditions, with temperatures ranging from 35 to 37 degrees Celsius, and some locations exceeding 37 degrees. Relative humidity is expected to drop to 40-45%.

By April 5, the heat will expand northward to Thanh Hoa, where temperatures may reach 35-37 degrees Celsius, with some areas surpassing 38 degrees and humidity remaining low at 40-45%.

In the southeastern region, hot weather will persist on April 4-5, with temperatures commonly between 35 and 36 degrees Celsius, and some places exceeding 36 degrees. Humidity levels are expected to range from 45-50%.

The meteorological agency warns that the heatwave from Thanh Hoa to Quang Ngai, as well as in the southeastern region, may continue for several days.

It also cautions that forecast temperatures may differ from actual outdoor conditions by 2-4 degrees Celsius, or even higher, depending on surface factors such as concrete and asphalt.

With high temperatures and low humidity, there is an increased risk of fires and explosions in residential areas due to rising electricity demand. Prolonged exposure to extreme heat may also lead to dehydration and other health risks.

Bao Anh